1. Field of the Invention
This invention relates to cardiac physiology. More particularly, this invention relates to the evaluation of electrical propagation in the heart.
2. Description of the Related Art
The meanings of certain acronyms and abbreviations used herein are given in Table 1.
TABLE 1Acronyms and AbbreviationsBSECGBody Surface ECGECGElectrocardiogramEGMElectrogramTEATime Ensemble AveragingUEGMUnipolar ElectrogramVFFVentricular Far Field
Cardiac arrhythmias such as atrial fibrillation are an important cause of morbidity and death. Commonly assigned U.S. Pat. No. 5,546,951, and U.S. Pat. No. 6,690,963, both issued to Ben Haim and PCT application WO 96/05768, all of which are incorporated herein by reference, disclose methods for sensing an electrical property of heart tissue, for example, local activation time, as a function of the precise location within the heart. Data are acquired with one or more catheters having electrical and location sensors in their distal tips, which are advanced into the heart. Methods of creating a map of the electrical activity of the heart based on these data are disclosed in commonly assigned U.S. Pat. No. 6,226,542, and U.S. Pat. No. 6,301,496, both issued to Reisfeld, which are incorporated herein by reference. As indicated in these patents, location and electrical activity is typically initially measured on about 10 to about 20 points on the interior surface of the heart. These data points are then generally sufficient to generate a preliminary reconstruction or map of the cardiac surface. The preliminary map is often combined with data taken at additional points in order to generate a more comprehensive map of the heart's electrical activity. Indeed, in clinical settings, it is not uncommon to accumulate data at 100 or more sites to generate a detailed, comprehensive map of heart chamber electrical activity. The generated detailed map may then serve as the basis for deciding on a therapeutic course of action, for example, tissue ablation, to alter the propagation of the heart's electrical activity and to restore normal heart rhythm.
Catheters containing position sensors may be used to determine the trajectory of points on the cardiac surface. These trajectories may be used to infer motion characteristics such as the contractility of the tissue. As disclosed in U.S. Pat. No. 5,738,096, issued to Ben Haim, which is incorporated herein in its entirety by reference, maps depicting such motion characteristics may be constructed when the trajectory information is sampled at a sufficient number of points in the heart.
Electrical activity at a point in the heart is typically measured by advancing a multiple-electrode catheter to measure electrical activity at multiple points in the heart chamber simultaneously. A record derived from time varying electrical potentials as measured by one or more electrodes is known as an electrogram. Electrograms may be measured by unipolar or bipolar leads, and are used, e.g., to determine onset of electrical propagation at a point, known as local activation time.
Sensors in a cardiac chamber may detect far-field electrical activity, i.e., the ambient electrical activity originating away from the sensors, which can distort or obscure local electrical activity, i.e., signals originating at or near the sensor location. Commonly assigned U.S. Patent Application Publication No. 2014/0005664 of Govari et al., which is herein incorporated by reference, discloses distinguishing a local component in an intracardiac electrode signal, due to the tissue with which the electrode is in contact from a remote-field contribution to the signal, and explains that a therapeutic procedure applied to the tissue can be controlled responsively to the distinguished local component.
U.S. Patent Application Publication No. 2014/0187991 of Thakur et al. proposes a method for mapping a cardiac chamber by sensing activation signals of intrinsic physiological activity with a plurality of electrodes disposed in or near the cardiac chamber. The method includes isolating R-wave events in the activation signals, generating a far-field activation template representative of a far-field activation signal component based on the R-wave events, and filtering the far-field activation template from the activation signals to identify near-field activation signal components in the activation signals.